When someone views/partakes in an action in a video game that is so amazing and/or awe-inspiring that that the individual makes an orgasm sound.

Alternative:
Gaymgasm/Gaymegasm: When two or more gamers of the same sex simultaneously have a gamegasm over the same action in-game.

Example:
Gamer 1: *watches "Life in the West" video of Red Dead Redemption* *makes orgasm/sex noises*
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Later that day:
Gamer 1: Dude I just watched a trailer for Red Dead Redemption, everything in that video gave me a gamegasm!
Gamer 2: Some of the stuff in that game looks freaking sweet!